The soybean is a commercially very important plant which has an extraordinary number and variety of uses. It is used as a source of both food for domestic animals and human beings, and as a source of oil, which itself has many important uses. The soybean cake or meal, that remains after processing the beans for oil, is a high-protein foodstuff used extensively in livestock and poultry rations. It is an excellent protein with respect to most of the essential amino acids and also a good source of vitamins of the B-complex. The botanical name for the soybean is Glycine max, the genus to which the variety belongs being identified by the first Latin word and the species to which it belongs by the second Latin word.
The soybean is an annual summer legume, and is, like other members of the botanical family Leguminosae such as peas and beans, characterized by having pods each of which (in the case of the soybean) has from 2 to 4 round or oval seeds (beans). Soybeans are classified as simple fruits since they are derived from a single ovary, and can be reproduced from single seeds contained within a pod of the plant. Classification structure and nature of legumes is described by Robbins et al., Botany: An Introduction to Plant Science, John Wiley & Sons, Inc. (1950).
The soybean is an erect, branching plant, with trifoliate leaves borne one to a node, resembling in its early growth the ordinary field bean. It grows to a height ranging from 2 ft. to 31/2 ft. or more. Nearly all varieties are pubescent; that is, the stems, leaves and pods of the plant are covered with short, fine, brown or gray hairs. The mature pods range in color from very light tan to shades of gray, brown and black, and the seeds themselves may be colored in shades of yellow, green, brown or black, or may be speckled. The seeds have an oil content ranging from 15% to 25%, and a protein content ranging from 30% to 50%.
There are a number of ways in which soybeans may be classified, including by color, plant type, plant habit, and seed characteristics.
Color: Soybeans have leaves which range in color from light green to dark green; the pod color may range anywhere from light tan to black, as aforesaid; and the seed coat color may range from yellow to black. Finally, the pubescence color may be either gray or brown.
Plant Type: Soybeans may also be classified as slender, bushy or intermediate.
Plant Habit: Soybeans may be classified, as regards habit, as being determinate or indeterminate.
Seed Characteristics: The seeds of soybeans may be characterized according to shape--whether they are spherical or elongate--and according to size; and also according to whether they are wrinkled or smooth.
A mature soybean plant comprises roots, stems, petioles, leaflets, pods and seeds. Prior to maturity a soybean plant has small inconspicuous flowers, which may be either white or purple.